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1

This is all over the place. Can you separate out 1 - the questions you want answered, and 2 - the sentences you want us to check on. I fear this is either style advice or too elementary.
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MitchAug 1 '12 at 19:31

1

We don't generally use "in" with colors, except in very specific cases: "Does this shirt come in green?" but not "*This shirt is in green."
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MarthaªAug 1 '12 at 20:31

Bob's answer is a good one. In the first case, I would recommend removing the 'in's from the second sentence to make it less wordy. It does lose the parallelism with the first sentence, but I think that's acceptable in this case.

There are five items in four different colors. One is red, another is yellow,
another is green, and the others are black.

A better structure, in my opinion, works off of the second case:

There are five items in four different colors. Two of the items are black,
and the three others are yellow, blue, and green, respectively.

I think it's pretty clear what you're trying to say here, i.e. that the three remaining items correspond to the three remaining colours. I mean, if five items are in four colours, and you mention that two of them are black and list three other colours, it's pretty clear that this is the case.